The present invention relates to radio receivers, such as cellular handsets and pagers, and particularly to battery operated radio receivers having power save by reducing the active reception time.
Communication systems between a remote (base) station, and a mobile station or terminal, such as cellular phones and pagers, commonly Include a current-saving mode, usually called an Idle or Standby mode, in order to save battery power in the mobile terminals. In these terminals, the Standby mode consists of a relatively long xe2x80x9csleepxe2x80x9d interval in which most of the terminal blocks of the mobile station are deactivated, and a relatively short xe2x80x9creceptionxe2x80x9d interval In which the terminal is enabled to receive from the base station transmitted data, usually a paging or a broadcast message, which may be intended for the terminal. The mobile station checks whether this message is intended for itself, and according to its contents, decides an further actions, like going to the sleep phase, continuing the reception phase, etc. Prior to the data detection in the reception phase, there is a pre-conditioning or synchronization period in which the receiver pre-conditions the receive path for data detection, e.g., synchronizes to the correct gain, frequency, DC offset, timing, and/or to other parameters the receiver may need. Examples for such parameters are equalizer tap gains when an equalizer is employed, or xe2x80x9cfingersxe2x80x9d gains and delays when a xe2x80x9cRAKExe2x80x9d receiver is employed,
In the present systems of the foregoing type, the batteries provided in the receivers are generally capable of operating the receiver for a total Standby time of approximately 200 hours, and a total Talk time of approximately 2 hours before battery-recharging is required. It would be very desirable to increase this Standby time by decreasing the current drawings on the battery during this time.
Various techniques have been developed for reducing current drain in battery-operated receivers, as described, for example, in U.S. Pat. Nos. 5,708,971 and 3,737,322, but there is still a need to further decrease current drain particularly during the long xe2x80x9cStandbyxe2x80x9d period.